Conventionally, as a mechanical seal device for sealing a special liquid such as a chemical which dose not allow the use of a special high-temperature pump or an O ring, there is known a mechanical seal device which includes a metal bellows. In addition, there is known a mechanical seal device which is configured as a cartridge-type mechanical seal device in order to improve assembly and make the mechanical seal device compact (Patent Documents 1 and 2).
With reference to FIG. 5, a conventional cartridge-type mechanical seal device will be described. FIG. 5 is a schematic cross-sectional view for explaining the configuration of a mechanical seal device according to the conventional art.
A mechanical seal device 100 shown in FIG. 5 is provided between a housing 200 such as the casing of a pump or the like and a rotary shaft 300, and seals the inside A of the housing 200 from the outside (air side) B. The mechanical seal device 100 has a seal cover 102 which is attached to the housing 200 and a sleeve 103 which is fit on the rotary shaft 300. In the seal cover 102, a fixed ring 104 as an annular member, a bellows 105, and a spring 106 are provided. In the sleeve 103, a rotary ring 107 as an annular member is provided.
The seal cover 102 and the sleeve 103 are attached to the housing 200 and the rotary shaft 300 respectively such that the fixed ring 104 and the rotary ring 107 are in contact with each other. The fixed ring 104 and the rotary ring 107 are slidably in contact with each other to form an annular seal surface S, and the seal state is thereby formed. The bellows 105 and the spring 106 are provided so as to be stretchable in an axial direction, and bias the fixed ring 104 toward the rotary ring 107 to thereby enhance the adhesion of the seal surface S.
Herein, in the cartridge-type mechanical seal device 100 described above, its cost is reduced and the cartridge-type mechanical seal device is made compact by reducing the number of ridges of the metal bellows 105 which requires high manufacturing cost, and an insufficient biasing force is supplemented by using the spring 106. In addition, the spring 106 is disposed on the outer peripheral side of the bellows 105 in order to avoid exposure to a liquid.
However, in the above cartridge configuration in which the bellows 105 and the spring 106 are arranged in a radial direction, a reduction in radial dimensions is limited, and hence attachment space is restricted and the range of devices to which the mechanical seal device can be applied is limited. In addition, slurry having a high density contained in a target liquid to be sealed is pushed outward by a centrifugal force caused by the rotation of the rotary shaft 300, and is pushed into a groove between the ridges on the inner peripheral side of the bellows 105. When the mechanical seal device is used for a long time period, there is a possibility that the slurry deposited in the groove affects stretchability of the bellows 105.    [Patent Document 1] WO 2010/004809    [Patent Document 2] WO 2010/123025